Question on Volume and Density?

Question

What is the volume in Liters of a 7.85x10(to the 4th power) g sample of copper if the density of copper is 8.90g/mL?

One penny weighs 2.50 grams and has a density of 6.94g/mL. If you drop 50 oennies into a beaker with 250.0 mL of water in it, what will be the total volume in the beaker? What will be the total mass in the beaker?


I have no idea how to do these two problems. Any help would be wonderful!

Answer 1

Sorry for my english but i am italian.
1)From the density i Know that 1 mL weights 8.90 g so 8820 mL weights 7.85.10^4 ( 1 : 8.90 = x : 7.85.10^4).
8820 mL are 8.82 L
2)50 pennies weights 125g
1 mL : 6.94g = x mL : 125g
x= 18 mL
250+18=268 mL
Since 250 mL of water = 250g

Total mass = 250+125= 375 g

Answer 2

The density of copper is 8.90 g/mL so 1 gram of copper will occupy 1 / 8.9 mL of volume. Now multiply this by the amount of copper given, 7.85 X 10 ^ -4 (10 raised to the power of -4) which gives you the volume in mL. divide that by 1000 to get the value in Litres.

7.85 X 10 ^ -4 X 1
------------------------ = 0.882 X 10 ^ -7 L
8.9 X 1000
(rounded off to three decimals)

Next question:

1 penny weighs 2.5 grams and the density is 6.94 g/mL. So, each penny has a volume of 2.5/6.94 mL.

50 pennies will be 50 X 2.5 /6.94 mL = 125/6.94 = 18.01 mL. Add this to 250 to get the total Volume = 268.01 mL

Total mass in the beaker will be 250 + 125 = 375 grams since the density of water is 1 g/mL unless otherwise stated.